Toluene is a toxic air pollutant and a common constituent emitted from industrial processes including chemical manufacturing operations, painting, and petroleum refining. We previously developed a new biofilter system the degradation of acetone and MEK. In this study, we evaluate the optimum EBRT to achieve an effective elimination capacity (EC) with smaller filter bed volume. In addition, we optimized the operation conditions for toluene degradation using the same biofilter system.